1. Field of the Invention
The present invention relates to a plasma lighting system using microwave, and more particularly, to a high temperature operation type electrodeless bulb of a plasma lighting system, which is capable of maintaining the temperature in the electrodeless bulb at a high level, and a plasma lighting system having the same.
2. Description of the Related Art
In general, a plasma lighting system (PLS) is a lighting system in which a high frequency is generated using a high frequency oscillator (magnetron) mainly used for a microwave oven, and such microwave converts a buffer gas in the bulb into a plasma state to enable a metal compound to continuously emit light, thereby providing light with excellent light intensity without an electrode.
FIG. 1 is a vertical cross sectional view showing one example of a conventional plasma lighting system. FIG. 2 is a front view showing a coupled state of an electrodeless bulb and a bulb motor in a conventional plasma lighting system. FIG. 3 is a graph for explaining a S3 filter effect.
As shown therein, the plasma lighting system includes: a magnetron 20 installed inside a casing 10, for generating microwave; a high voltage generator 30 boosting the voltage of utility AC power and supplying it to the magnetron 20; a wave guide 40 connected to an outlet of the magnetron 20 and transmitting microwave generated in the magnetron 20; an electrodeless bulb 50 generating light by using enclosed materials in a plasma state by microwave energy; a resonator 60 covered on the front side of the wave guide 40 and electrodeless bulb 50, for intercepting the microwave and passing the light generated from the electrodeless bulb 50; a reflecting shade 70 receiving the resonator 60 and focus-reflecting the light generated in the electrodeless bulb 50 straightly; a dielectric mirror 80 installed inside the resonator 60 at the rear of the electrodeless bulb 50 in order to pass the microwave and reflect the light; and a cooling fan 90 placed at one side of the casing 10 and cooling the magnetron 20 and the high voltage generator 30.
The electrodeless bulb 50 is constructed with a luminous unit 51 having a predetermined inner volume, made of quartz, having enclosed luminous materials, for example, diatomic sulfur molecules (S2), an inert gas, a discharge catalyst, sodium, etc. in order to emit lights by being turned into a plasma state, and placed outside the casing 10, and a supporting unit 52 integrally extended from the luminous unit 51 and supported by the inner side of the casing 10.
One end of the supporting unit 52 is coupled to a rotation shaft 111 of a bulb motor 110 by using a connecting member 100 of a hollow rod shape. The supporting unit 52 of the electrodeless bulb 50 is inserted and bonded and coupled to the connecting member 100, while the rotation shaft 111 of the bulb motor 110 is secured by screws.
In the drawings, unexplained reference numeral 120 is a fan motor.
The operation of the conventional plasma lighting system will be described below.
According to a command of a controller, the magnetron 20 oscillates due to a high voltage, and generates microwaves having a very high frequency. As the generated microwaves are emitted into the resonator 60 through the wave guide 40, the inert gas enclosed inside the electrodeless bulb 50 is excited. In this procedure, the luminous materials continuously generate plasma and generate light having an inherent emission spectrum.
The light generated from the electrodeless bulb 50 is reflected by the reflecting shade 70 and the dielectric mirror 80 and lights up a space. At this time, the bulb motor 110 is also supplied with a power, and as the rotation shaft 111 rotates the electrodeless bulb 50 at a predetermined speed while rotating, to thus prevent an electric field from being focused on the luminous unit 51 of the electrodeless bulb 50, as well as preventing an air current around the luminous unit 51 from being stagnated, thereby preventing damage of the electrodeless bulb 50. Further, the fan motor 120 cools the magnetron 20 and the high voltage generator 30 through the air introduced by rotating the cooling fan 90.
In such a plasma lighting system, as shown in FIG. 3, the diatomic sulfur molecules (S2) enclosed in the luminous unit 51 are uniformly distributed over the entire part of the luminous unit 51, while triatomic sulfur molecules (S3) are greatly increased in density around inner walls of the luminous unit 51. Such triatomic sulfur molecules (S3) are dark-brown materials, and act as a filter for intercepting light This is called the S3 filter effect (Transport and equilibrium in molecular plasmas: the sulfur lamp, C. W. Johnston, 2003, 59p). As a result, the S3 filter effect reduces the emission efficiency of the luminous unit 51, so there is a need to alleviate this reduction.
Further, because quartz used as the luminous unit 51 is expensive glass, there is a need to substitute quartz with materials that exhibit the functions superior to those of quartz and are more economical.